According to STD-B44 “Transmission system for advanced wide band digital satellite broadcasting” of the Association of Radio Industries and Businesses (ARIB), which is an industry organization carrying out standards development regarding mobile phones and digital broadcasting in Japan, it is necessary to transmit an IP packet including a Network Time Protocol (NTP) format by suppressing delay variation, and to place the IP packet in the first slot among slots assigned to each Type Length Value (TLV) stream ID.
FIG. 1 shows a configuration of a TLV frame described in ARIB STD-B44. A detailed explanation will be omitted, however, Transmission and Multiplexing Configuration Control (TMCC) information is written in the 165 bytes at the end of each slot (Slot #1, #2, . . . #24) for a main signal. The TMCC information comprises information related to transmission control, such as the transmission stream allocation for each slot and the relationship between transmission schemes and each slot. One TVL frame comprises 120 slots. The configuration of a TLV frame is not limited to only the configuration described in the drawing.
According to ARIB STD-B44, in the case of switching transmission schemes, etc., the TMCC information is required to transmit the post-switching information two frames prior to the main signal. That is, in order to advance the TMCC information for the switching by two frames, it is necessary to delay the main signal from that TMCC information by two frames.
FIG. 2 shows the relationship between the TMCC information for switching and the main signal delayed by two frames. For example, pointer/slot information described in the TMCC information of the first slot of frame (N−2) describes the front or head position of the first packet included in the first slot of frame N and the end position of the last packet in the first slot of frame N. Since one frame is approximately 33 milliseconds (ms) (33.0464716 ms), transmission timings of the TMCC information and the main signal indicated by the pointer/slot information described in that TMCC information are in a relationship where the output of the main signal is delayed approximately 66 ms with respect to the transmission timing of that TMCC information.
As a result, a delay corresponding to two frames (approximately 66 ms) occurs between a time written in an NTP packet multiplexed on a TLV slot and a time when transmitting that TLV slot.
Since this delay lengthens a period between a receiving time of a video/audio packet at a receiver and a starting time of decoding/displaying by approximately 66 ms, a buffer size of the receiver for buffering data during such period increases.
Since the start of decoding/displaying the video and audio at the receiver is performed based on a system time, the delay in broadcasting increases, thereby degrading real-time properties.
Therefore, the realization of a multiplexing device and a multiplexing method capable of solving the delay between a time written in the NTP packet and a timing for transmitting the TLV slot has been desired.